Shape memory alloy actuators are solid state actuators that may be utilized to provide a motive force for motion of one object, such as an attached component, relative to another object, such as a base structure to which the attached component is attached via the shape memory alloy actuator. Shape memory alloy actuators may generate the motive force via a phase change within a shape memory alloy element thereof, and this phase change may be initiated by a temperature change. As an example, the shape memory alloy element may transition from a martensite state to an austenite state upon being heated and also may transition from the austenite state to the martensite state upon being cooled.
Heating of the shape memory alloy element historically has been accomplished utilizing a heating assembly, such as a resistive heating element and/or an inductive heating element. In contrast, cooling of the shape memory alloy element historically has been accomplished via convective cooling with a heat transfer fluid stream. The heating generally may be performed relatively quickly; however, the cooling often takes a significantly longer amount of time and thus may be rate-limiting to an overall cycle time of the shape memory alloy actuator (e.g., a time needed to transition the shape memory alloy element from the martensite state to the austenite state and back to the martensite state or vice versa).
In general, a rate of convective cooling may be increased by increasing a surface area for heat transfer between a body to be cooled and a heat transfer fluid stream that flows in fluid contact with the body to be cooled. As an example, cooling fins may be affixed to the body to be cooled and/or may be defined by the body to be cooled.
While such an approach may be effective under certain circumstances, it may be difficult, or even impossible, to effectively and reliably implement in the context of a shape memory alloy element. As an example, the shape memory alloy element may experience significant physical deformation upon transitioning between the martensite state and the austenite state, and this physical deformation may make it difficult, or even impossible, to operatively attach cooling fins to the shape memory alloy element. As another example, a shape memory alloy that defines the shape memory alloy element may have a low thermal conductivity, and cooling fins that might be defined by the shape memory alloy element itself may not be effective at improving convective cooling of the shape memory alloy element. Thus, there exists a need for improved shape memory alloy actuators with heat transfer structures, for actuated assemblies that include the improved shape memory alloy actuators, and/or for methods of manufacturing the improved shape memory alloy actuators.